U.S. patent number 8,092,870 [Application Number 12/410,529] was granted by the patent office on 2012-01-10 for preparation of metal oxide thin film via cyclic cvd or ald.
This patent grant is currently assigned to Air Products and Chemicals, Inc.. Invention is credited to Moo-Sung Kim, Xinjian Lei, Daniel P. Spence, Sang-Hyun Yang.
United States Patent |
8,092,870 |
Kim , et al. |
January 10, 2012 |
**Please see images for:
( Certificate of Correction ) ** |
Preparation of metal oxide thin film via cyclic CVD or ALD
Abstract
A cyclic deposition process to make a metal oxide film on a
substrate, which comprises the steps: introducing a metal
ketoiminate into a deposition chamber and depositing the metal
ketoiminate on a heated substrate; purging the deposition chamber
to remove unreacted metal ketominate and any byproduct; introducing
an oxygen-containing source to the heated substrate; purging the
deposition chamber to remove any unreacted chemical and byproduct;
and, repeating the cyclic deposition process until a desired
thickness of film is established.
Inventors: |
Kim; Moo-Sung (Sungnam,
KR), Lei; Xinjian (Vista, CA), Spence; Daniel
P. (San Diego, CA), Yang; Sang-Hyun (Suwon,
KR) |
Assignee: |
Air Products and Chemicals,
Inc. (Allentown, PA)
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Family
ID: |
40839635 |
Appl.
No.: |
12/410,529 |
Filed: |
March 25, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100075067 A1 |
Mar 25, 2010 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61044270 |
Apr 11, 2008 |
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Current U.S.
Class: |
427/576; 427/569;
427/248.1 |
Current CPC
Class: |
C23C
16/45553 (20130101); C23C 16/409 (20130101) |
Current International
Class: |
H05H
1/24 (20060101); C23C 16/00 (20060101) |
Field of
Search: |
;427/576,569,248.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 849 789 |
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Oct 2007 |
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EP |
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1 983 073 |
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Oct 2008 |
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EP |
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2 065 364 |
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Jun 2009 |
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EP |
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2002305194 |
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Oct 2002 |
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JP |
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20030000423 |
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Jan 2003 |
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KR |
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20070105280 |
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Oct 2007 |
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KR |
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Other References
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Primary Examiner: Gambetta; Kelly M
Attorney, Agent or Firm: Rossi; Joseph D. Chase; Geoffrey
L.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This patent application claims the benefit of U.S. Provisional
Patent Application Ser. No. 61/044,270 filed 11 Apr. 2008.
Claims
The invention claimed is:
1. In a cyclic deposition process for the formation of ternary
metal oxide films wherein a plurality of precursors are
sequentially introduced into a deposition chamber, vaporized and
deposited on a substrate under conditions for forming said ternary
metal oxide film, the improvement which comprises: employing a
first metal ketoiminate as a first precursor; employing an
oxygen-containing source; employing a second metal ketoiminate as a
second and different precursor; and, employing an oxygen-containing
source, wherein one of the first or second ketoiminates is selected
from the group represented by structure A: ##STR00003## wherein M
is a divalent Group 2 metal selected from the group consisting of
calcium, magnesium, strontium, and barium; wherein R.sup.1 is
selected from the group consisting of alkyl, fluoroalkyl,
cycloaliphatic, having from 1 to 10 carbon atoms, and aryl having
from 6 to 12 carbon atoms; R.sup.2 is selected from the group
consisting of hydrogen, alkyl, alkoxy, cycloaliphatic, having from
1 to 10 carbon atoms, and aryl having 6 to 12 carbon atoms; R.sup.3
is selected from the group consisting of alkyl, fluoroalkvl,
cycloaliphatic, having from 1 to 10 carbon atoms, and aryl having 6
to 12 carbon atoms; R.sup.4 is a C.sub.2-3 linear or branched
alkylene bridge with or without chiral carbon atom, thus making a
five- or six-membered coordinating ring to the metal center;
R.sup.5-6 are individually selected from the group consisting of
alkyl, fluoroalkyl, cycloaliphatic, having from 1 to 10 carbon
atoms, and aryl having 6 to 12 carbon atoms, and they can be
connected to form a ring containing carbon, oxygen, or nitrogen
atoms; and the other of the first or second ketoiminate is selected
from a group represented by structure B: ##STR00004## wherein M is
a tetra-valent metals selected from the group consisting of
titanium, zirconium, and hafnium; wherein R.sup.7 is selected from
the group consisting of alkyl, fluoroalkyl, cycloaliphatic, having
from 1 to 10 carbon atoms, and aryl having 6 to 12 carbon atoms;
R.sup.8-9 is selected from the group consisting of hydrogen, alkyl,
alkoxv, cycloaliphatic, having from 1 to 10 carbon atoms, and aryl
having 6 to 12 carbon atoms; R.sup.10 is a C.sub.2-3 linear or
branched alkylene bridge with or without chiral carbon atom, thus
making a five- or six-membered coordinating ring to the metal
center.
2. The process of claim 1 wherein the metal ketoiminates are
delivered via direct liquid delivery by dissolving the ketoiminates
in a solvent or a solvent mixture to prepare a solution with a
molar concentration from 0.01 to 2 M.
3. The process of claim 1 wherein the solvent is selected from the
group consisting of aliphatic hydrocarbons, aromatic hydrocarbons,
linear or cyclic ethers, esters, nitriles, alcohols, amines,
polyamines, organic amides and mixtures thereof.
4. The process of claim 3 where the solvent is selected from group
consisting of tetrahydrofuran (THF), mesitylene, dodecane,
N-methylpyrrolidinone (NMP), and mixtures thereof.
5. The process of claim 1 where the ternary metal oxide is
strontium titanate.
6. The process of claim 1 wherein the cyclic deposition process is
a cyclic chemical vapor deposition process.
7. The process of claim 1 wherein the cyclic deposition process is
an atomic layer deposition process.
8. The process of claim 1 wherein the pressure in the deposition
chamber is from 50 mtorr to 100 torr and the temperature in said
deposition chamber is below 500.degree. C.
9. The process of claim 1 wherein the oxygen-containing source is
selected from the group consisting of oxygen, oxygen plasma, water,
water plasma, ozone, nitrous oxide and mixtures thereof.
10. The process of claim 1 wherein the resulting ternary metal
oxide film is exposed to a rapid thermal annealing or plasma
treatment to densify the resulting multicomponent metal oxide
film.
11. The process of claim 1 wherein the metal ketoiminate of the
structure A is selected from the group consisting of
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2,
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NEt.sub.2)Me}.sub.2,
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NMe.sub.2)Me}.sub.2, and
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NEt.sub.2)Me}.sub.2; the
structure B metal ketoiminate is selected from the group consisting
of Ti{MeC(O)CHC(NCH.sub.2CH.sub.2O)Me}.sub.2 and
Ti{MeC(O)CHC(NCH(Me)CH.sub.2O)Me}.sub.2.
12. The process of claim 1 wherein R.sup.1 is selected from the
group consisting of alkyl, fluoroalkyl, cycloaliphatic, having from
1 to 6 carbon atoms.
13. The process of claim 1 wherein R.sup.2 is selected from the
group consisting of hydrogen, alkyl, alkoxy, cycloaliphatic, having
from 1 to 6 carbon atoms.
14. The process of claim 1 wherein R.sup.3 is selected from the
group consisting of alkyl, fluoroalkyl, cycloaliphatic, having from
1 to 6 carbon atoms.
15. The process of claim 1 wherein R.sup.5-6 are individually
selected from the group consisting of alkyl, fluoroalkyl,
cycloaliphatic, having from 1 to 6 carbon atoms.
16. The process of claim 1 wherein R.sup.7 is selected from the
group consisting of alkyl, fluoroalkyl, cycloaliphatic, having from
1 to 6 carbon atoms.
17. The process of claim 1 wherein R.sup.8-9 is selected from the
group consisting of hydrogen, alkyl, alkoxy, cycloaliphatic, having
from 1 to 6 carbon atoms.
18. In a cyclic deposition process for the formation of multiple
component metal oxide films wherein a plurality of precursors are
introduced into a deposition chamber, vaporized and deposited on a
substrate under conditions for forming said multiple component
metal oxide film, the improvement which comprises: employing at
least two metal ketoiminates dissolved in a solvent or a solvent
mixture to prepare a solution; and employing an oxygen-containing
source, wherein the at least two metal ketoiminates comprise a
metal ketoiminate represented by structure A and another metal
ketoiminate represented by structure B, the solutions each has a
molar concentration from 0.01 to 2 M; wherein the structures A and
B are defined below: ##STR00005## wherein M is a divalent Group 2
metal selected from the group consisting of calcium, magnesium,
strontium, and barium; wherein R.sup.1 is selected from the group
consisting of alkyl, fluoroalkyl, cycloaliphatic, having from 1 to
10 carbon atoms, and aryl having 6 to 12 carbon atoms; R.sup.2 is
selected from the group consisting of hydrogen, alkyl, alkoxy,
cycloaliphatic, having from 1 to 10 carbon atoms, and aryl having 6
to 12 carbon atoms; R.sup.3 is selected from the group consisting
of alkyl, fluoroalkyl, cycloaliphatic, having from 1 to 10 carbon
atoms, and aryl having 6 to 12 carbon atoms; R.sup.4 is a C.sub.2-3
linear or branched alkylene bridge with or without chiral carbon
atom, thus making a five- or six-membered coordinating ring to the
metal center; R.sup.5-6 are individually selected from the group
consisting of alkyl, fluoroalkyl, cycloaliphatic, having from 1 to
10 carbon atoms, and aryl having 6 to 12 carbon atoms, and they can
be connected to form a ring containing carbon, oxygen, or nitrogen
atoms; ##STR00006## wherein M is a tetra-valent metals selected
from the group consisting of titanium, zirconium, and hafnium;
wherein R.sup.7 is selected from the group consisting of alkyl,
fluoroalkvl, cycloaliphatic, having from 1 to 10 carbon atoms, and
aryl having 6 to 12 carbon atoms; R.sup.8-9 is selected from the
group consisting of hydrogen, alkyl, alkoxv, cycloaliphatic, having
from 1 to 10 carbon atoms, and aryl having 6 to 12 carbon atoms;
R.sup.10 is a C.sub.2-3 linear or branched alkylene bridge with or
without chiral carbon atom, thus making a five- or six-membered
coordinating ring to the metal center.
19. The process of claim 18 wherein the solution of metal
ketoiminates is delivered via direct liquid injection.
20. The process of claim 18 wherein the solvent is selected from
the group consisting of aliphatic hydrocarbons, aromatic
hydrocarbons, linear or cyclic ethers, esters, nitriles, alcohols,
amines, polyamines, organic amides and mixtures thereof.
21. The process of claim 20 where the solvent is selected from
group consisting of tetrahydrofuran (THF), mesitylene, dodecane,
N-methylpyrrolidinone (NMP) and their mixture thereof.
22. The process of claim 18 where the multiple component metal
oxide is strontium titanate.
23. The process of claim 18 wherein the cyclic deposition process
is a cyclic chemical vapor deposition process.
24. The process of claim 18 wherein the structure A metal
ketoiminate is selected from the group consisting of
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2,
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NEt.sub.2)Me}.sub.2,
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NMe.sub.2)Me}.sub.2, and
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NEt.sub.2)Me}.sub.2.
25. The process of claim 18 wherein the structure B metal
ketoiminate is selected from the group consisting of
Ti{MeC(O)CHC(NCH.sub.2CH.sub.2O)Me}.sub.2 and
Ti{MeC(O)CHC(NCH(Me)CH.sub.2O)Me}.sub.2.
26. The process of claim 18 wherein R.sup.1 is selected from the
group consisting of alkyl, fluoroalkyl, cycloaliphatic, having from
1 to 6 carbon atoms.
27. The process of claim 18 wherein R.sup.2 is selected from the
group consisting of hydrogen, alkyl, alkoxy, cycloaliphatic, having
from 1 to 6 carbon atoms.
28. The process of claim 18 wherein R.sup.3 is selected from the
group consisting of alkyl, fluoroalkyl, cycloaliphatic, having from
1 to 6 carbon atoms.
29. The process of claim 18 wherein R.sup.5-6 are individually
selected from the group consisting of alkyl, fluoroalkyl,
cycloaliphatic, having from 1 to 6 carbon atoms.
30. The process of claim 18 wherein R.sup.7 is selected from the
group consisting of alkyl, fluoroalkyl, cycloaliphatic, having from
1 to 6 carbon atoms.
31. The process of claim 18 wherein R.sup.8-9 is selected from the
group consisting of hydrogen, alkyl, alkoxy, cycloaliphatic, having
from 1 to 6 carbon atoms.
Description
BACKGROUND OF THE INVENTION
High-dielectric constant (high-k) thin films such as SrTiO.sub.3
(STO) and Ba(Sr)TiO.sub.3 (BST) have been widely investigated as
one of the promising capacitor materials of the next generation
dynamic random access memory (DRAM) devices. For this application,
very conformal deposition with respect to the film thickness and
composition is required over a 3-dimensional (3-D) capacitor
structure.
Recently, atomic layer deposition (ALD) processes have been
developed to meet these requirements using various source
materials. ALD is one of the most promising techniques based upon
its unique self-limiting deposition mechanism. In general, ALD can
show low deposition temperature, excellent step coverage over high
aspect ratio features, good thickness uniformity and accurate
thickness control by means of layer-by-layer film deposition.
Plasma enhanced ALD (PEALD) has also been developed due to its
advantages, such as higher deposition rate and lower deposition
temperature, while keeping advantages of ALD.
Regarding precursor materials, for example, STO thin film can be
deposited with Sr bis(2,2,6,6-tetramethyl-3,5-heptanedionato),
i.e., (Sr(thd).sub.2) as a Sr precursor, TTIP(Ti-tetraisopropoxide)
as a Ti precursor and O.sub.3, O.sub.2 plasma or H.sub.2O vapor as
an oxidant. Especially regarding Sr precursor, although
Sr(thd).sub.2 and some other Sr precursors have been widely
studied, those precursors still have limitations, such as too low
vapor pressure, thermal decomposition at low temperature, etc.
Therefore, a demand still remains for developing an appropriate
Group 2 or Group 4 precursor and corresponding deposition process,
most importantly finding Group 2 and 4 complexes that have similar
ligands, which make them compatible in terms of physical and
chemical properties, such as melting point, solubility,
vaporization behavior and reactivity towards a semi-fabricated
semiconductor surface. Consequently, the Group 2 and 4 complexes
can be dissolved in a solvent and delivered into a reaction chamber
to deposit a multi-component metal oxide film for DRAM
applications.
BRIEF SUMMARY OF THE INVENTION
The present invention is a cyclic deposition process to make a
metal oxide film on a substrate, which comprises the steps:
introducing a metal ketoiminate into a deposition chamber and
depositing the metal ketoiminate on a heated substrate; purging the
deposition chamber to remove unreacted metal ketominate and any
by-products; introducing an oxygen-containing source to the heated
substrate; purging the deposition chamber to remove any
by-products; and, repeating the cyclic deposition process until a
desired thickness of film is established.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is Thermo Gravimetric Analysis/Differential Scanning
Calorimetry (TGA/DSC) graphs of
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2 (solid
line) and Ti{MeC(O)CHC(NCH.sub.2CH.sub.2O)Me}.sub.2 (dotted line),
indicating these two complexes are compatible due to their very
similar vaporization behavior.
FIG. 2 is TGA/DSC graphs of
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NMe2)Me}.sub.2 (solid line) and
Ti{MeC(O)CHC(NCH(Me)CH.sub.2O)Me}.sub.2 (dotted line),
demonstrating these two complexes are compatible due to their same
melting point, as well as similar vaporization behavior.
FIG. 3 is temperature dependence of PEALD of depositing SrO using
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2 and O.sub.2
plasma.
FIG. 4 shows the resulting SrO thickness dependence with the number
of deposition cycles at a temperature of 250.degree. C. via PEALD
using Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2 and
O.sub.2 plasma.
FIG. 5 shows the resulting SrO thickness dependence with the Sr
precursor Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2
pulse time at 250.degree. C. via PEALD.
FIG. 6 is temperature dependence of thermal ALD of depositing SrO
using Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2 and
ozone.
FIG. 7 is temperature dependence of thermal ALD of depositing SrO
using Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NMe.sub.2)Me}.sub.2 and
ozone.
FIG. 8 is demonstration of direct liquid injection stability
through back pressure monitoring prior to the injector orifice. A)
0.1 M strontium precursor
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NMe.sub.2)Me}.sub.2 dissolved in
mesitylene and B) 0.1M strontium precursor
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NMe.sub.2)Me}.sub.2 dissolved in
10% (wt) tetrahydrofuran in dodecane.
DETAILED DESCRIPTION OF THE INVENTION
The invention describes a method for making a metal or
multicomponent metal oxide film, such as strontium oxide, titanium
oxide or strontium titanate, which may be used, for example, in
fabricating semiconductor devices. The method disclosed herein
provides a metal or multicomponent metal oxide film that has a
dielectric constant substantially higher than that of either
conventional thermal silicon oxide, silicon nitride, or
zirconium/hafnium oxide dielectric.
The method disclosed herein deposits the metal oxide films using
cyclic chemical vapor deposition (CCVD) or atomic layer deposition
(ALD) techniques. In certain embodiments, the metal oxide films are
deposited via a plasma enhanced ALD (PEALD) or plasma enhanced CCVD
(PECCVD) process. In this embodiment, the deposition temperature
may be relatively low, such as 200 to 600.degree. C., to control
the specifications of film properties required in DRAM or other
semiconductor applications. The method disclosed herein forms the
metal oxide films using metal ketoiminate precursors and an oxygen
source.
A typical process is described as follows: Step 1. Contacting
vapors of a metal ketoiminate precursor with a heated substrate to
chemically sorb the precursor on the heated substrate; Step 2.
Purging away any unsorbed ketoiminate precursors and any
by-products; Step 3. Introducing an oxygen source on the heated
substrate to react with the sorbed metal ketoiminate precursor;
and, Step 4. Purging away any unreacted oxygen source and
by-products.
In one embodiment, the ketoiminate precursor is selected from the
group represented by the structure:
##STR00001##
wherein M is a divalent Group 2 metal including calcium, magnesium,
strontium, barium. A variety of organo groups may be employed, as
for example wherein R.sup.1 is selected from the group consisting
of alkyl, fluoroalkyl, cycloaliphatic, having from 1 to 10 carbon
atoms, preferably a group containing 1 to 6 carbon atoms, and an
aryl group having from 6 to 12 carbon atoms; R.sup.2 is selected
from the group consisting of hydrogen, alkyl, alkoxy,
cycloaliphatic, having from 1 to 10 carbon atoms, preferably a
group containing 1 to 6 carbon atoms, and an aryl group having from
6 to 12 carbon atoms; R.sup.3 is selected from the group consisting
of alkyl, fluoroalkyl, cycloaliphatic, having from 1 to 10 carbon
atoms, preferably a group containing 1 to 6 carbon atoms, and an
aryl group having from 6 to 12 carbon atoms; R.sup.4 is a C.sub.2-3
linear or branched alkyl bridge with or without chiral carbon atom,
thus making a five- or six-membered coordinating ring to the metal
center, Exemplary alkyl bridges include but are not limited to
--(CH.sub.2).sub.2--, --(CH.sub.2).sub.3--, --CH(Me)CH.sub.2--,
--CH.sub.2CH(Me)-; R.sup.5-6are individually selected from the
group consisting of alkyl, fluoroalkyl, cycloaliphatic, having from
1 to 10 carbon atoms, preferably a group containing 1 to 6 carbon
atoms, and an aryl group having from 6 to 12 carbon atoms, and they
can be connected to form a ring containing carbon, oxygen, or
nitrogen atoms. The structure A metal ketoiminate preferably is
selected from the group consisting of
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2,
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NEt.sub.2)Me}.sub.2,
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NMe.sub.2)Me}.sub.2, and
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NEt.sub.2)Me}.sub.2.
In another embodiment, a ketoiminate precursor is selected from the
group represented by the structure:
##STR00002##
wherein M is a tetra-valent Group 4 metals, including titanium,
zirconium, or hafnium. A variety of organo groups may be employed
as for example wherein R.sup.7 is selected from the group
consisting of alkyl, fluoroalkyl, cycloaliphatic, having from 1 to
10 carbon atoms, preferably a group containing 1 to 6 carbon atoms,
and an aryl group having from 6 to 12 carbon atoms; R.sup.8-9 is
selected from the group consisting of hydrogen, alkyl, alkoxy,
cycloaliphatic, having from 1 to 10 carbon atoms, preferably a
group containing 1 to 6 carbon atoms, and an aryl group having from
6 to 12 carbon atoms; R.sup.19 is a C.sub.2-3 linear or branched
alkyl bridge with or without chiral carbon atom, thus making a
five- or six-membered coordinating ring to the metal center.
Exemplary alkyl bridges, include, but are not limited to:
--(CH.sub.2).sub.2--, --(CH.sub.2).sub.3--, --CH(Me)CH.sub.2--,
--CH.sub.2CH(Me)-.
The deposition methods disclosed herein may involve one or more
purge gases. The purge gas, used in the steps of purging away
unreacted reactant and/or by-products, is an inert gas that does
not react with the precursors and may preferably be selected from
the group consisting of Ar, N.sub.2, He, and mixture thereof.
Depending upon the deposition method, the purge gas, such as Ar, is
supplied into the reactor, e.g., at a flow rate of about 10 to 2000
sccm for about 0.1 to 1000 seconds, thereby purging the unreacted
material and any byproduct that remain in the chamber.
The temperature of the substrate in the reactor, i.e., a deposition
chamber, may preferably be below about 600.degree. C. and more
preferably below about 500.degree. C., and the process pressure may
preferably be from about 0.01 Torr to about 100 Torr, and more
preferably from about 0.1 Torr to about 5 Torr.
The oxygen source in Step 3 can be an oxygen-containing source
selected from the group consisting of oxygen, oxygen plasma, water,
water plasma, ozone, nitrous oxide and mixture thereof.
The respective step of supplying the precursors and the oxygen
source gases may be performed by varying the duration of the time
for supplying them to change the stoichiometric composition of the
resulting metal oxide film. For multicomponent metal oxide films, a
ketominate precursor selected from the structures "A" or "B" can be
alternately introduced in step 1 into the reactor chamber.
A direct liquid delivery method can be employed by dissolving the
ketoiminate in a suitable solvent or a solvent mixture to prepare a
solution with a molar concentration from 0.01 to 2 M, depending the
solvent or mixed-solvents employed. The solvent employed in the
invention may comprise any compatible solvents or their mixture
including aliphatic hydrocarbons, aromatic hydrocarbons, linear or
cyclic ethers, esters, nitriles, alcohols, amines, polyamines, and
organic amides, preferably a solvent with high boiling point, such
as mesitylene (b.p. 164.degree. C.) or N-methyl-2-pyrrolidinone
(b.p. 202.degree. C.) and more preferably a solvent mixture
consisting of a polar solvent such as tetrahydrofuran (THF) or
N-methylpyrrolidinone (NMP) and a non-polar solvent, such as
dodecane.
The plasma-generated process comprises a direct plasma-generated
process in which plasma is directly generated in the reactor, or a
remote plasma-generated process in which plasma is generated out of
the reactor and supplied into the reactor.
The present invention also contemplates a cyclic deposition process
for the formation of ternary metal oxide films wherein a plurality
of precursors are sequentially introduced into a deposition
chamber, vaporized and deposited on a substrate under conditions
for forming a said ternary metal oxide film.
The present invention further contemplates that the resulting metal
oxide films can be exposed to a plasma treatment to densify the
resulting multicomponent metal oxide film.
The present invention is useful as a method for deposition of metal
oxide or multiple component metal oxide thin films, which are
utilized in a semiconductor device structures. With this invention,
a metal oxide film can be formed with an atomic layer deposition
ALD or CCVD method, depending on the process condition.
An ALD growth proceeds by exposing the substrate surface
alternatively to the different precursors. It differs from CVD by
keeping the precursors strictly separated from each other in the
gas phase. In an ideal ALD window where film growth proceeds by
self-limiting control of surface reaction, the pulse length of each
precursor, as well as the deposition temperature, have no effect on
the growth rate, if the surface is saturated.
A CCVD process can be performed at a higher temperature range, than
an ALD process, where in CCVD a precursor decomposes. CCVD is
different from the traditional CVD in terms of precursor
separation. Each precursor is sequentially introduced and totally
separated in CCVD, but in traditional CVD, all reactant precursors
are introduced to the reactor and induced to react with each other
in the gas phase. The common attribute of CCVD and traditional CVD
is that both relate to the thermal decomposition of precursors.
The present invention is also useful as a method of depositing
metal oxide films using plasma-enhanced an ALD (PEALD) technique to
make a semiconductor device structure. Metal oxide films can be
prepared by a CVD and a typical thermal ALD; however, using PEALD,
the deposition rate can be increased, and it is known that PEALD
enhances the film properties and widens the process window.
EXAMPLE 1
This example describes a CCVD deposition of SrO using a Sr
ketoiminate precursor,
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2, dissolved
in mesitylene, and O.sub.2 plasma. The deposition temperature range
is 200.about.400.degree. C., and a DLI (direct liquid injection),
with a vaporizor used to deliver the Sr precursor. The deposition
chamber pressure ranges around 1.5 Torr, depending upon the gas
flow rates. The dip tube side of the canister, containing the Sr
precursor dissolved in a liquid (mesitylene), is connected to an
injector valve in the DLI system, and pressurized N.sub.2
(.about.30 psig) is connected to the other side of the canister to
push the liquid. One cycle of CCVD of SrO consists of 5 steps. 1.
Injection of a 0.1M solution of Sr precursor in mesitylene; opening
an injection valve for a few milliseconds will provide Sr precursor
containing vapor in the vaporizor; 2. Sr pulse: introducing Sr
precursor vapor to the deposition chamber; and Sr precursor is
chemically sorbed on the heated substrate; 3. Ar purge: purging
away any unsorbed Sr precursor with Ar; 4. O.sub.2 plasma pulse:
introducing O.sub.2 into the deposition chamber while applying
radio frequency (RF) power (50 Watts (W) in this case) to react
with sorbed Sr precursor on the heated substrate; and, 5. Ar purge:
purging away any unreacted O.sub.2 and by-products with Ar.
In this example, SrO film was obtained, showing a deposition
temperature dependence of the SrO film. The injection time was 2
milliseconds, the Sr pulse time was 5 seconds, the Ar purge time
after Sr pulse was 10 seconds, the O.sub.2 plasma pulse time was 3
seconds, and the Ar purge time after O.sub.2 plasma pulse was 10
seconds. Repeat for 150 cycles.
The results are depicted in FIG. 3, in which the ALD process window
was up to .about.320.degree. C.
EXAMPLE 2
In this example, SrO films were deposited, via conditions as
follows: the injection time of 0.1M solution of Sr precursor,
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2, in
mesitylene was 2 milliseconds, the Sr precursor pulse time was 5
seconds, the Ar purge time after Sr pulse was 10 seconds, the
O.sub.2 plasma pulse time was 3 seconds, and the Ar purge time
after O.sub.2 plasma pulse was 10 seconds. The wafer temperature is
250.degree. C. The experiments were conducted for 50, 150, 250,
300, and 600 cycles respectively. The results are depicted in FIG.
4, showing a linear dependence of film thickness vs number of
cycles, a characteristic feature of ALD processes.
EXAMPLE 3
In this example, SrO films were deposited via conditions as
follows: the injection time of 0.1M solution of Sr precursor,
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2, in
mesitylene was 2 milliseconds, the Ar purge time after Sr precursor
pulse was 10 seconds, the O.sub.2 plasma pulse time was 3 seconds,
and the Ar purge time after O.sub.2 plasma pulse was 10 seconds.
The wafer temperature is 250.degree. C. The Sr pulse time varies
from 1 to 7 seconds. The results are depicted in FIG. 5, showing a
saturation curve around 5 seconds for the Sr pulse, suggesting a
typical self-limiting ALD process under these conditions.
EXAMPLE 4
This example describes an ALD or CCVD deposition of SrO using a Sr
ketoiminate precursor,
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2, dissolved
in mesitylene and ozone. The deposition temperature range is
200.about.425.degree. C., and a DLI (direct liquid injection), with
a vaporizor used to deliver the Sr precursor. The deposition
chamber pressure ranges around 1.5 Torr, depending upon the gas
flow rates. The dip tube side of the canister, containing the Sr
precursor dissolved in a liquid (mesitylene), is connected to an
injector valve in the DLI system, and pressurized N.sub.2
(.about.30 psig) is connected to the other side of the canister to
push the liquid. One cycle of CCVD of SrO consists of 5 steps. 1.
Injection of a 0.1M solution of Sr precursor in mesitylene; opening
an injection valve for a few milliseconds will provide Sr precursor
containing vapor in the vaporizor; 2. Sr pulse: introducing Sr
precursor vapor to the deposition chamber; and Sr precursor is
chemically sorbed on the heated substrate; 3. Ar purge: purging
away any unsorbed Sr precursor with Ar; 4. Ozone pulse: introducing
ozone into the deposition chamber; and, 5. Ar purge: purging away
any unreacted ozone and any by-products with Ar.
In this example, SrO film was obtained, showing a deposition
temperature dependence of the resulting SrO film deposition rates.
The injection time was 2 milliseconds, the Sr pulse time was 5
seconds, the Ar purge time after Sr pulse was 10 seconds, the ozone
pulse time was 5 seconds, and the Ar purge time after ozone pulse
was 10 seconds.
The results are depicted in FIG. 6 in which the ALD process window
was up to .about.340.degree. C.
EXAMPLE 5
This example describes an ALD or CCVD deposition of SrO using a Sr
ketoiminate precursor,
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NMe.sub.2)Me}.sub.2, dissolved in
10% (wt) of THF in dodecane and ozone. The deposition temperature
range is 200.about.425.degree. C., and a commercial DLI (direct
liquid injection) system was used to deliver the Sr precursor. The
deposition chamber pressure ranges around 1.5 Torr, depending upon
the gas flow rates. The dip tube side of the canister, containing
the Sr precursor dissolved in 10% (wt) of THF in dodecane, is
connected to an injector valve in the DLI system, and pressurized
N.sub.2 (.about.30 psig) is connected to the other side of the
canister to push the liquid. In this case the injector valve is
always open, and the liquid mixture of Sr precursor and above
solvent is vaporized through a nozzle (atomizer). Ar carrier gas
helps vaporization. One cycle of ALD or CCVD of SrO consists of 4
steps. 1. Injection of a 0.1M solution of
Sr{.sup.tBuC(O)CHC(NCH(Me)CH.sub.2NMe.sub.2)Me}.sub.2 in 10% (wt)
of THF in dodecane to deliver the Sr precursor vapors to the
deposition chamber; and the Sr precursor is chemically sorbed on
the heated substrate; 2. Ar purge: purging away any unsorbed Sr
precursor with Ar; 3. ozone pulse: introducing ozone into the
deposition chamber; and, 4. Ar purge: purging away any unreacted
ozone and any by-products with Ar.
In this example, SrO film was obtained, showing a deposition
temperature dependence of the resulting SrO film thickness. The
injection time of the Sr pulse time was 5 seconds, the Ar purge
time after Sr pulse was 5 seconds, the ozone pulse time was 5
seconds, and the Ar purge time after ozone pulse was 5 seconds.
The results are depicted in FIG. 7 in which the ALD process window
was up to .about.320.degree. C.
EXAMPLE 6
In this example, a direct liquid injection vaporizer system was
monitored as strontium precursor,
Sr{.sup.tBuC(O)CHC(NCH.sub.2CH.sub.2NMe.sub.2)Me}.sub.2, dissolved
in solvent was vaporized through the heated injector. In this case,
the injector was heated to 185.degree. C., the carrier gas flow
rate was 500 sccm of helium gas, a precursor-solvent mass flow rate
of 1 g/min. The pressure monitor was located prior to the injector,
directly in the carrier gas stream.
The results in FIG. 8 show a very stable back pressure over the run
time of .about.3 hours using a combined solvent of 10% (wt) of THF
in dodecane. In contrast, the same concentration of strontium
precursor dissolved in mesitylene shows a continual increase in
back pressure as additional precursor was flowing through the
injector system. The combined effect of the higher boiling point
solvent of dodecane with the additional solubility gained through
addition of THF enabled stable injector performance over the
lifetime of this flow test.
* * * * *